You embark on a hiking trip on Mt. Kilimanjaro (altitude = 19,000 ft; Atmospheric air pressure = 379 mmHg).mHg). As you ascend, what are you likely to notice about your breathing?
A. You need to work to exhale, using your muscles to decrease your thoracic size beyond what is normal
B. You need to work harder to inhale, expanding your thoracic size beyond what is normal
C. Both would happen
D. Neither would happen

B. You need to work harder to inhale, expanding your thoracic size beyond what is normal

Explanation:

To breathe, we need a difference between the atmospherical pressure and the intrapulmonary pressure. The first one is the pressure that the external air does to enter our lungs when we inhale, it has to be bigger than the intrapulmonary pressure, which is the pressure that is applied to our lungs by our diaphragm when this contracts to expel the air that is in our lungs.

As we ascend in a mountain, the atmospherical pressure is lower, so it is harder for the air to go into our lungs. As a result, we need to expand our thoracic size beyond normal to force the air into our lungs.